The present invention belongs to a technical field covering optical components such as lenses. More particularly, the present invention relates to a durable optical component having a multilayer light reflection preventing film or the like having high adhesion force, and to a method of manufacturing the optical component.
Glass has been used as a material for optical components such as lenses. On the other hand, in recent years, optical components made of plastics such as polymethyl methacrylate (PMMA), etc. have been found in wide use because they are light in weight, low-cost and highly producible.
One of characteristics generally required for such optical components is a good light reflection preventing property (low optical reflectivity). Ordinarily, a light reflection preventing film is formed on a surface of such optical components.
A single-layer film formed by using a low-refractive-index material such as magnesium fluoride (MgF2) is generally used as a light reflection preventing film formed on optical component surfaces. As a light reflection preventing film with better light reflection preventing property, a multilayer light reflection preventing film (multiple coating light reflection preventing film) is known in which a single layer or multiple layers of a low-refractive-index material and a single layer or multiple layers of a high-refractive-index material are alternately formed.
Optical components made of plastics having a multilayer light reflection preventing film, however, have a problem that adhesion property between a substrate (i.e., the optical component made of a plastic) and the multilayer light reflection preventing film is low, that is, the durability is not sufficiently high.
Ordinarily, a multilayer light reflection preventing film is formed by a vapor-phase deposition process such as vacuum deposition.
In a vapor-phase deposition process, the temperature of the substrate rises to expand the substrate even though heating of the substrate is not performed. In particular, to form a multilayer light reflection preventing film, a process in which a plurality of layers are successively formed and film forming of a high-refractive-index material is performed by using a comparatively large amount of energy is ordinarily performed in consideration of productivity, etc. If such process is used, the substrate temperature becomes so high that the substrate expands substantially largely.
When the substrate is taken out of the film forming apparatus into atmosphere after film forming of a multilayer light reflection preventing film has been completed, it is abruptly cooled to shrink.
However, the substrate made of a plastic, particularly an acrylic material typified by PMMA and the multilayer light reflection preventing film formed on the substrate differ in thermal expansion coefficient from each other, and the thermal expansion coefficient of the multilayer light reflection preventing film formed on the substrate is smaller than that of the substrate. Therefore, the multilayer light reflection preventing film cannot follow the deformation of the substrate due to its shrinkage when the substrate is taken out of the film forming apparatus into atmosphere after the completion of film forming, resulting in damage to the multilayer light reflection preventing film and large strain in the film.
As a result, the adhesion force of the multilayer light reflection preventing film is reduced. Also, the adhesion force gradually reduces with time. Thus, the durability of the optical component having the multilayer light reflection preventing film is substantially reduced.
A first object of the present invention is to provide an optical component and a manufacturing method thereof free from the above-described problem of the conventional art, i.e., an optical component in which a multilayer light reflection preventing film is formed on a substrate made of a plastic which is light in weight, low-cost, and highly producible, in which the adhesion force of the film is high, and which has improved durability as well as a good light reflection preventing property, and a method of manufacturing the optical component.
A second object of the present invention is to provide an optical component and a manufacturing method free from the above-described problem of the conventional art, i.e., an optical component in which a substrate made of a plastic which is light in weight, low-cost, and highly producible is used, in which a plurality of films for a multilayer light reflection preventing film or the like are formed on the substrate by vacuum deposition, in which the adhesion force of the film is high, and which has improved durability, and a method of manufacturing the optical component.
In order to attain the first object described above, the first aspect of the present invention provides an optical component comprising a substrate made of a resin material, a thick silicon oxide film formed on a surface or the substrate, and a multilayer light reflection preventing film formed on the thick silicon oxide film, and having at least one layer of a low-refractive-index material and at least one layer of a high-refractive-index material being alternately formed.
Preferably, the substrate is made of an acrylic resin material.
Preferably, the thick silicon oxide film is formed by introducing oxygen during film forming by vacuum deposition so that a preset elasticity is imparted to the thick silicon oxide film.
Preferably, directions of internal stresses in each adjacent pair of the thick silicon oxide film and the respective layers constituting the multilayer light reflection preventing film are different from each other.
Preferably, a thickness of an impurity existing on the surface of the substrate is 0.2 nm or less.
And, preferably, the multilayer light reflection preventing film is formed by vacuum deposition in such a manner that the thick silicon oxide film is formed by vacuum deposition on the surface of the substrate, and thereafter, melting of a low-refractive-index material and a high-refractive-index material provided as film forming materials for the multilayer light reflection preventing film is performed.
Also, in order to attain the first object described above, the second aspect of the present invention provides an optical component comprising a substrate made of a resin material, a silicon oxide film formed on a surface of the substrate, and a multilayer light reflection preventing film formed on the silicon oxide film, and having at least one layer of a low-refractive-index material and at least one layer of a high-refractive-index material being alternately formed, wherein a preset elasticity is imparted to the silicon oxide film by introducing oxygen during film forming by vacuum deposition.
In addition, the second aspect of the present invention provides a method of manufacturing an optical component which comprises a substrate made of a resin material, a silicon oxide film formed on a surface of the substrate, and a multilayer light reflection preventing film formed on the silicon oxide film, and having at least one layer of a low-refractive-index material and at least one layer of a high-refractive-index material being alternately formed, comprising forming the silicon oxide film by vacuum deposition, and introducing oxygen during film forming of the silicon oxide film by vacuum deposition to impart a preset elasticity to the silicon oxide film.
Preferably, the substrate is made of an acrylic resin material.
Preferably, directions of internal stresses in each adjacent pair of the silicon oxide film and the respective layers constituting the multilayer light reflection preventing film are different from each other.
Preferably, a thickness of an impurity existing on the surface of the substrate is 0.2 nm or less.
Further, preferably, the multilayer light reflection preventing film is formed by vacuum deposition in such a manner that the silicon oxide film is formed by vacuum deposition on the surface of the substrate, and thereafter, melting of a low-refractive-index material and a high-refractive-index material provided as film forming materials for the multilayer light reflection preventing film is performed.
In order to attain the second object described above, the third aspect of the present invention provides an optical component comprising a substrate made of a resin material, and a plurality of films formed by vacuum deposition, wherein directions of internal stresses in each adjacent pair of the plurality of films are different from each other.
Preferably, a thickness of an impurity existing on a surface of the substrate is 0.2 nm or less.
Preferably, the plurality of films are formed in such a manner that after one film of the plurality of films has been formed on a surface of the substrate, melting of film forming materials other than a film forming material for one film formed on the surface of the substrate is performed.
Furthermore, in order to attain the second object described above, the fourth aspect of the present invention provides an optical component comprising a substrate made of a resin material, and a plurality of films formed by vacuum deposition, wherein a thickness of an impurity existing on a surface of the substrate is 0.2 nm or less.
Preferably, the plurality of films are formed in such a manner that after one film of the plurality of films has been formed on the surface of the substrate, melting of film forming materials other than a film forming material for one film formed on the surface of the substrate is performed.
Further, the fourth aspect of the present invention provides an method of manufacturing an optical component in which a plurality of films are formed by vacuum deposition on a surface of a substrate made of a resin material, the method comprising forming one film of the plurality of films on the surface of the substrate, and performing melting of film forming materials other than a film forming material for one film formed on the surface of the substrate after film forming of one film of the plurality of films on the surface of the substrate.